1. Field of the invention
The present invention relates to an adjustment device for a movable wall of an injection molding machine, more particularly one, which will help lengthen the service life of the injection molding machine.
2. Brief Description of the Prior Art
Referring to FIG. 1, a conventional plastic injection molding machine 1 includes a bed 11, a heating device 12, a mold 13, a movable wall 14, a fixed wall 15, a rear seat 16, a mold closing device 17, and four guide rods 18. The guide rods 18 are secured to the rear seat 16 at first ends thereof, and securely joined to the fixed wall 15 at the other ends thereof. The movable wall 14 is supported on and movable along the guide rods 18. The mold 13 includes male female halves, which are secured on the movable wall 14, and the fixed wall 15 respectively. The heating device 12 is positioned on the bed 11 for melting plastic materials, and injecting the materials into the mold 13. The mold closing device 17 is connected to both the rear seat 16 and the movable wall 14 for moving the movable wall 14 along the guide rods 18, and it can be equipped with oil hydraulic cylinders or toggles.
Furthermore, the movable wall 14 is equipped with bushings 141 around the guide rods 18. Because the intermediate portions of the guide rods 18, along which the movable wall 14 will move, aren't propped with other articles, and the mold closing device 17, the movable wall 14, and the male (female) halves of the mold 13 together are very heavy in weight, axes of the guide rods 18 and bushings 141 of the movable wall 14, through which the guide rods 18 are passed, will change their direction, causing the orientation of the guide rods 18 in relation to the bushings 141 to undesirably change as shown in FIG. 2. Consequently, the bushings 141 will touch the guide rods 18 in an abnormal way, and wear down too rapidly.
Referring to FIG. 3, to overcome the above problem, adjustment devices 19 are connected to two ends of a bottom of the movable wall 14. The adjustment devices 19 are movable along guide rails 111 secured on the upper side of the bed 11, and each includes a fixed sloping block 191, a movable sloping block 192, and a bolt 193; the movable sloping block 192 is on the guide rails 111 with a sloping side thereof facing up while the fixed sloping block 191 has a sloping bottom touching the upper sloping side of the movable sloping block 192; the bolt 193 is connected to both the movable sloping block 192 and the fixed sloping block 191, used for changing position of the movable sloping block 192 relative to the fixed sloping block 191. Therefore, the two ends of the movable wall 14 can be adjusted in height, and the movable wall 14 will be propped up by means of the adjustment devices 19, maintaining the original direction of the axes of the guide rods 18 and the bushings 141 of the movable wall 14, and preventing the bushings 141 from touching the guide rods 18 in an abnormal manner to wear down too rapidly. Consequently, the bushings 141 have longer service life.
However, the bushings 141 will be prevented from touching the guide rods 18 to wear down in an abnormal manner only when the movable wall 14 is still. When the movable wall 14 is moving along the guide rods 18, it will still move up and down because the guide rails 111 aren't one hundred percent smooth owing to limitation on precision of manufacturing. Consequently, the axes of the guide rods 18 and the bushings 141 of the movable wall 14 will change their direction, and the bushings 141 will touch the guide rods 18 in an abnormal manner, and wear down too rapidly.